<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h2 id="one">
    你好
</h2>
<button type="button" onclick="New()">
点击
</button>
<script>
    function success(text) {
        var textarea = document.getElementById('test-response-text');
        textarea.value = text;
    }

    function fail(code) {
        var textarea = document.getElementById('test-response-text');
        textarea.value = 'Error code: ' + code;
    }

    var request = new XMLHttpRequest(); // 新建XMLHttpRequest对象

    request.onreadystatechange = function () { // 状态发生变化时，函数被回调
        if (request.readyState === 4) { // 成功完成
            // 判断响应结果:
            if (request.status === 200) {
                // 成功，通过responseText拿到响应的文本:
                return success(request.responseText);
            } else {
                // 失败，根据响应码判断失败原因:
                return fail(request.status);
            }
        } else {
            // HTTP请求还在继续...
        }
    }

    // 发送请求:
    request.open('GET', 'https://www.liaoxuefeng.com/api/categories');
    request.send();

    alert('请求已发送，请等待响应...');

</script>
</body>
</html>